1. Field of the Invention
The present invention relates to methods of preparation and cutting of contact lenses. In particular it relates to a method of precisely orienting and affixing a device to determine the position of a contact lens during fabrication of that lens. Present methods include marking the lens (or the lens mount) and aligning this mark with a mark on a holding device. Another method is to attach the lens to its mount in a specific manner. These methods are less precise, more cumbersome, and more variable than the method which is the subject of this patent. After these initial steps, additional cuts must be made so that the lens orients upon the eyeball in a proper and comfortable fashion. This involves various cuts that require precise knowledge of the angular orientation of the lens. These cuts also involve 180 degree flips or rotations of the lens in order to perform an exact duplicate cut on a reverse side of the lens or movement from one offset collet to another without displacement of orientation.
This second section of the lens preparation, up till now, was usually done without any sophisticated marking or holding equipment. A lens was usually placed in a radiuscope and the major axes of the lens curvature or meridians were marked out by hand. This led to imprecision, the usual allowable tolerance being 2 to 10 degrees. The orientation for the axes marks for the cutters with the lens blocked to an arbor was also done by hand, the cutter visually positioning the lens marks in order to perform the necessary positioning and repositioning of the lens. A more precise and consistent method of marking and orienting the lens is necessary to reduce imprecision and the cost of discarded lenses.
2. Description of the Prior Art
The following is a discussion of patents for inventions related to the present invention, but not disclosing it as such, either singly or in combination.
U.S. Pat. No. 3,100,955 issued to Kratt discloses an apparatus for producing contact lenses comprising a lens blank holding tool which maintains an orientation flange around the lens during the cutting and polishing operations. The holding tool insures maintenance of a proper optical axis for the surfaces of the lens as to axial alignment.
U.S. Pat. No. 3,501,842 issued to Beasley discloses a method and apparatus for blocking a multifocal lens blank in a predetermined relationship to the desired optical properties of the lens according to a particualr prescription. The block is then secured to the lens blank during the grinding and polishing or edging operations.
U.S. Pat. No. 3,662,040 issued to Urbach et al. describes a technique for making multifocal contact lenses employing a conventional radius turning lathe having two supports, one for the lens blank and the other for the tool. The tool is rotated about an axis fixed on its support to that its point describes a circle while the blank is held fixed in a support movable about a center traverse or perpendicular to the tool axis. By the disclosed technique multifocal areas of the lens may be provided that fall on a common axis.